1. Field of the Invention
The present invention relates to photographic apparatus and more particularly to a camera head for alternately maintaining a focussing screen and a film holder in an operative position with respect to the camera.
2. Description of the Prior Art
In photography so-called view or press cameras are replete. In fact, such cameras trace their roots to the infancy of photography. Nevertheless and significant advances wrought in the photographic arts notwithstanding, such cameras have never lost their appeal or their usefulness. They are widely employed in photographic studios or on photographic copying systems. Advantages such cameras offer are, for instance, that they are provided with ground glass focussing screens placed directly to intersect the optical axis of the lens of such cameras and identical in size to the format of the film used. Hence, they permit a photographer to compose his picture carefully and precisely, though inverted from the image rendered by the film.
Examples of such cameras may be found, for example, in U.S. Pat. No. 493,365 issued to Law and Shakespeare on Mar. 14, 1893 and U.S. Pat. No. 3,896,464 issued to Galvin on July 22, 1975. A device for alternately holding a focussing screen and a film holder is the subject of U.S. Pat. No. 3,786,735 issued to Seiden on Jan. 22, 1974.
All these have in common that they show focussing screens movable with respect to supporting structure to make possible placement of a film holder or the like. Thus in U.S. Pat. No. 493,365 a ground glass is shown mounted on a camera back by a plurality of pivotable links and movable from a focussing position in direct engagement with the camera to a position remote therefrom by links pivotable by rotating a shaft.
In U.S. Pat. No. 3,896,464 a view camera is shown having a ground glass viewing screen resiliently maintained against its back by means of spring biased arms. A film holder may be mounted on the camera by grasping the frame of the ground glass screen, lifting or tilting it off the camera back against the bias of the spring and sliding the film holder between the screen and camera back where it is then held by the tension of the arms to which the screen is attached. A somewhat similar arrangement is disclosed by U.S. Pat. No. 3,786,735 where a viewing screen is held in position by torsion bars. To place a film holder into the depicted apparatus the viewing screen is lifted away from the apparatus by grasping either one of two corners of the viewing screen and the film holder is then inserted into the resulting gap. It is held in position by the tension of the viewing screen torsion bars.
While prior art apparatus have been functioning properly, they have on the whole been inconvenient to use because proper positioning of viewing screens and film holders has involved cumbersome structures and awkward manipulations.